ImPasse Preamplifier

[RKH]

Me too...

Hi Jack,
I did send a PM requesting a board, populated with mosfets. Please let me know what the total tab is when you are ready.

Cheers,
Ryan

 

[RKH]

oops..

Sorry, I just read the post and will go via the techdiy site.

My apologies
Ryan

 

[jackinnj]

It's coming together -- showing the Maida regulator and the old RIAA section:

An externally hosted image should be here but it was not working when we last tested it.

If you want to really, really nicely clean up a PAS chassis, try carburetor cleaner.

 

[Tyimo]

Hi!
Could somebody tell me the technical parameters of this preamp?
Gain?
Output V?
In and output impedance? etc.

Thanks!
Tyimo

 

[SY]

Sure. Gain is 26dB (x20). Input is balanced or unbalanced, and depending on choice of transformer, 10k or 15k (can be made higher with a Zobel on the transformer secondary). Output is balanced, rated at 20V out (it was created for driving a balanced-in, unity-gain power amp). With a balanced load, output impedance is about 400 ohms. For a single ended load, the inverting output alone is taken.

 

[Tyimo]

Thanks SY!

 

[jackinnj]

OK -- took it for a test drive on the bench -- SY reported -68dB 2nd Harmonic, -92dB 3rd Harmonic. The one shown here measures -69 dB, -103 dB 3rd ! All of the R11, R12 resistors I purchased from Mouser came very tightly grouped around 15K.

I used Electro-Harmonix 6SN7 and 6922 -- the transformer I have is not center tapped so I wired the heater in series and raised one leg by the B+.

An externally hosted image should be here but it was not working when we last tested it.

 

[BDP]

Placed my order for the PC Board. Maybe I missed it, but are there any power supply/Maida regulator boards available. If not the parts count is low so perfboard would be easy enough.

BDP

 

[jackinnj]

I know that SY likes the non-Darlington version of the Maida for its simplicity. For the cost of another TIP transistor, LM329 and a couple of resistors you can get the souped up version. I showed a single-sided design here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=142420&highlight=

It's much easier to get the parts if you use 2 3-watt resistors to set the voltage.

I am going to have these boards burned as well.

 

[Coulomb]

Hello Jack, so will you be doing a second release of Preamp boards and will you be fixing the pinouts on the devices?

Anthony

 

[SY]

I know that SY likes the non-Darlington version of the Maida for its simplicity.

A MOSFET would no doubt also work well there.

 

[jackinnj]

Hello Jack, so will you be doing a second release of Preamp boards and will you be fixing the pinouts on the devices?

Anthony

Tell ya what, I'll send you the gerbers...

 

[BDP]

I am going to have these boards burned as well.

I will be watching for these regulator boards.

BDP

 

[av-trouvaille]

Jack,

Last week I have send you a mail via your site, after I noticed a pm here was not effective.
I am not in a hurry, just curious whether you did receive it.

Arjen.

 

[jackinnj]

I am out of the office until Thursday --

 

[jackinnj]

Instead of "Irish step dancers" these depletion MOSFETs remind me of the ladies on the IRT-Lexington Ave. subway going back uptown after a hard day in the canyons of Wall Street:

An externally hosted image should be here but it was not working when we last tested it.

 

[scranton]

That's poetry.

 

[Variac]

Fred and Ginger

 

[pchw]

Hi Jack,

The board arrived today. It is time to pay the "refund" that I owe you. Please let me know how do you want to proceed. I can submit a dummy order for this amount if this makes it easy for you.

Thanks!!

 

[wirewiggler]

Mounting cine mags

It looks like to the cinemags have to be mounted under the board to make pin1 line up. Due to the position of the ground 7 an shield 2&6 I don't think you could mount them on top, correct me if I am wrong.

Thanks
Bill